Please help me with urethane wave!!

C

Charlie D

Gentlemen:

It has been a year or so since my last post. I am the one that was painting panels off a ’55 Studebaker weekly at Vo Tech. They came out pretty good. The instructor painted all of them but two. The ones I was forced by a substitute to paint came out surprisingly nice. Of course everything I do during this first painting project is new to me. You guys have provided valuable feedback and foresight in the past and I need some more now.

I have been painting the shell while it is on the rotisserie. The last couple of days I have been color sanding the roof. It was sprayed with 1 coat of 1-1-1 epoxy primer as a seal coat. That was followed up by three medium coats of Restoration Shop Acrylic Urethane from TCP Global. It was painted about three weeks ago. It had orange peel and the first step was to remove it with 800 wet on one of those soft blocks. Yesterday I removed the 800 scratches with Trizact 1,500. On about a third of the roof I started removing the 1,500 scratches with a Mirca 3,000 6” pad.

I was so excited about how I could see the florescent lights and items sitting on the shelf being reflected in the area that had been damp-sanded with the 3,000. I took some pictures and thought to myself there was nothing to this new process and was feeling quite proud of myself. I then noticed that when I moved my head a little bit the edges of the florescent lights were not straight but had a series of waves/ripples in them. My enthusiasm tapered off pretty quickly and I realized that I must have a urethane wave situation.

I remember this being discussed on this forum as I follow it almost daily. All of my epoxy and primers are SPI. I do not know if I am going to attack this urethane wave or not. My wife told me today that I may not be happy knowing it is there. I think for displaying the car at old car meets and Studebaker events not many people of the general public are going to notice it. Of course if I enter it for judging the judges will probably pick it up.

I have researched this topic on the web and there were many excellent responses. Three individuals that I recognized from this site had posted excellent advice. They were Shine, Jim C. and BondoKing. I need to ask a few questions.

1. It appears that I need to basically block sand the urethane wave out of the panel. I am no stranger to block sanding as I have accumulated a few hundred hours on this car. My favorite block sanding block is a 21” adjustable flexible block that has the three stainless rods that can be inserted or removed. This block allows me to follow the contours of the Studebaker on the roof, deck lid, hood, etc. I use a SIM spray guide coat to highlight the lows. I have a short rubber block about 6 inches long that has nails on each side to attach the paper. I have three or four Dura blocks. Would I lightly mist the roof with the guide coat and then block sand with say a 400 or 600 roll of dry sandpaper on the blocks until all has been removed?

2. How long does the block have to be to remove the waves? Obviously the 2x4x1/2” soft block did not stay on the highs good enough to get rid of the waves but did remove the orange peel.

3. If I break through to the seal coat can I come back over the top of the block sanded acrylic urethane with a couple more coats of the acrylic urethane similar to shooting clear over sanded clear?

Thank you for your help. I have sprayed the remainder of the shell since I painted the roof and it has come out better with not as much orange peel. I will try to attach a couple of photos.

Charlie D.

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Looks like you have done a very nice job one I think you should be very proud of.

As for the wave, this can get kinda tricky. Not knowing how much clear you have put on this is how I would do it.

When I'm going for no wave I would apply 3-4 good coats of clear. The next day I would wetsand using a firm block with 800 & 1000gt then reclearing with 3-4 more. I would wait at least a week to allow the clear to breath out and get hard/cure. If you do it before the clear becomes firm it will still be soft and kinda rubber like where it can move just ever so slightly, think of that run drip on the edge of a panel you can move it with your fingernail (kinda rubbery) the surface of the clear is the same, it will move under the paper except you won't know it because you can't see it move but it is. If you wait and touch that drip later it will firm up and be easier to deal with just like the surface, make since?
Now after waiting at least a week I would hit it with 600/800wet with a hard-firm block and not using a whole lot if any pressure (the wetsand paper will suck itself to the panel). The least amount of pressure you apply the less likely you will be affecting the shape of the surface and will be just skimming the surface of the wave/peal. I will sand it keeping the contour of the surface like I was doing a final block sand criss cross and all. Once I get all that done I would repeat with the next grit (1000) using again hardly any pressure and a hard/firm block going in a differant direction then the previous grit and when all previous grit lines are gone on to the next grit (1500) and so forth till I get to my final grit (3000). While I am doing each grit I will give a day between each to allow the clear to breath and to give myself a break, it gets to your arms and eyes and I consentrat like crazy while doing it and that will tire you out. While I'm sanding I'm studying my feeling in my hand and can feel when I get to the point of no wave because the paper and the way it glides across the surface feel differant (just smooth no bumps) and grabs harder when you push and pull it draws itself into the clear with suction and that's why no real pressure is really needed. I use a series of blocks from 9in to 4in some hard rubber some soft, some people use a verity of blocks from plastic to hardwood but on a radious you need a firm but bendable enough to conform to the panels shape.

So going back to the beginning, not knowing how much clear you have put on do you feel you have enough too sand it again like that and not go through? Or if you didn't go through do you feel you would leave enough on to give good protection and longevity to the finnish?

I understand exactly what you are feeling when you see it, you have a I wish a woulda, coulda, shoulda feeling and are probably loosing sleep over it too (I have many a times), but you did a real nice job and don't need to beat yourself up over it when you get it outside you would be hard pressed to see it I'm sure. If I had to recommend the best way now to do it if you didn't clear twice like I mentioned would be to reclearing with 4 nice coats and keep the orange peal as small as possible (almost kinda dryspray) unless you can put it down smooth as glass because the bigger the orange peal the harder it is to get as glass smooth as you are looking for and will end up with wave again. The smaller the peal the easier it is to get glass smooth. To get the clear to lay down glass smooth you have to spray it on to just the point of a run and stop but that takes alot of practice and knowlage of everything you are using from equipment to material and how they act together, for the newer painters that's the reason i recommend i would rether see alittle dryer then overly wet clear when going for the smooth as glass look.

But from what i see you did yourself proud.
 
DATEC, it is interesting you should mention lack of sleep. I got to sleep at 3:30 this morning. I am not dealing with clear but rather single stage acrylic urethane. You have given me some advice that I can use. Thank you for describing the methodology you use to block the waves/peel. Before I tackle the waves I may go ahead and compound a couple square feet of the area that has been taken to 3000 grit. The rotisserie is on wheels so I can push it out of the garage and see what it looks like outdoors. I may decide that I can live with it the way it is. If not I can test your methodology on a small area to see if more of the wave can be smoothed out without a breakthrough to the seal coat.

Thank you for your help.
Charlie D.
 
Florescents show everything, you might be able to live with it outside.

In my opinion if you only have three coats of paint you have to either block it down and apply more color or possibly live with it. Not enough material to try and cut again. At least I wouldn't.

I use 16" durablocks with 800 or 1000 during the first go around. Klingspor wet/dry paper on sticky rolls. Then I swith to small soft blocks and regular 3m sleeves of grit from there.

Even 800 on a small block should have removed most of the wave. Not killer flat, but it should look pretty good.

Good luck.
 
3 coats then hard block with 800 . Then 2 medium wet coats. Shooting it heavy will put thanewave back in . 90% of diy guys will flood it on to get it wet. Turn your gun down and slow down .
 
Hard to tell from the pic, but some of the distortion in the reflection looks directional to me, which means it can be caused by sanding in one direction too much. I have seen this often in people that are strongly "handed," they prefer one hand very strongly over the other. This handedness produces a tendency to sand one angle of the crosshatch far more than the other. Those who don't switch hands very regularly must be mindful about how crosshatch sanding is being done, so far as to count sanding strokes in one direction and make sure an equal number are done in another direction. Problems associated with too much sanding in one direction are made worse by blocks that aren't 100% flat, blocks should be trued up on a flat surface like a thick piece of glass and sandpaper.
 
What I discribed can be put to use on solid colors also. I hope you find something in all that that will work for you. There are other additional tips for the final round of clear/color like thinning down the material a little to act like a flow coat but let's not go there. Try the area first and let us know what you deside.
 
Remember that when running the buffer to buff off all edges not into them, that could spell trouble fast.
 
Gentlemen:

Thank you so much for your help. Every post gave me an idea of what may have gone wrong. It is confession time I suppose. I researched color sanding a lot on the internet. One of the posts I came across the methodology that shop used was to 600 then 2,000 then buff. I thought to myself if I 800, 1,500 then 3,000 I would be OK. 68 Coronet R/T’s post got me thinking that maybe I was trying to cut corners and save some time (and my right arm). I know Shine has posted several times that he walks up the grit chain also.

I went to the supply house and bought some 1,000, 1,500, 2,000, 2,500 wet & dry paper. I taped off a section of the roof that had the wave in it. I used DATEC’s advice as far as methodology and used a small stiff rubber Dura-Block to wrap the paper on. I sanded with the various grits and finished up with the 6” Mirca 3,000 grit disk. The fluorescent lights are much smoother now.

I think the problem was sanding technique and not urethane wave. When I applied the paint to the roof I wanted to error on the side of orange peel rather than a run. I did not hammer it on thick as I had read Barry and Shine’s posts about too heavy of a coat can cause the wave. That was why I was so disappointed when I thought a wave had developed when I tried to be careful to prevent it.

I couple of other thoughts concerning why I think I had the problem. The Trizact 1,500 discs and I were not getting along very well. I am sure it is operator error rather than the discs. They started loading up pretty quick. They loaded up in the middle. As they loaded up I started putting more pressure on the outside of the disks to get to some new meat to sand with. This could have caused some of the sanding imperfections the first attempt. I think they would last a lot longer with a harder paint. My 3 week old paint may have been soft enough to come off on the discs easily and clog them up. I personally like the Mirka Abralon 6” 3,000 grit discs better. They make the Abralon in 4,000 grit and I am going to order some so that I can take the sanding to 4,000 grit before doing and compounding.

Another short cut and cost saving step I tried to get by with may be biting me in the butt. I purchased the cheap HF variable speed DA polisher. The first thing I did was to remove the 5 ¾ inch pad and put a better 5 inch pad on it. Several of the posts concerning that polisher recommended that. Well, my compressed air DA sander came with a PSA pad and I needed a hook & loop pad. I went and got the hook & loop pad that came on the cheap HF polisher and put it on the DA sander. I think I am getting some chatter with the Mirka disc. I am either going to buy a new 6”" pad or see if the Mirka comes in 5"” discs. If so I can put the new 5"” pad on the DA sander.

If you are still with me let me tell you about my spray gun and that DA sander. When I first started this project four years ago or so, I bought a used 60 gallon, 5 HP air compressor from a friend. I ran 40 feet of ½ copper line and silver soldered up a manifold to try to capture the water that would hopefully separate out of the air line. It was all hooked into a filter/separator with a regulator. After porting and polishing the engine heads with ¼ die grinders, sand blasting and used a borrowed DA sander from the neighbor, I realized the CFM from the compressor was a real bottleneck.

Eastwood advertised the Concourse gun as using less CFM than some others. They also advertised one of their DA sanders as requiring a lower CFM. My son bought them for father’s day with three tips. They are as advertised. The compressor can keep up with either of them. They are not as nice as a lot of other higher priced equipment but they work for me because of the air limitation I was faced with.

Once again guys, thank you for your help. I am a happy camper!!

Charlie D.
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Very Nice! Hope to see it finished soon. You should have seen my 1st job (30 some odd yrs ago) looked nowhere near that nice. Wish I had people in the field that could help guide me then, I had my Mom (she was a big help really) and support from Dad, but for the most part I had too learn the hard way, I'm glad my Dad didn't mind driving around with my "just learning paint jobs".

Dave
 
sanding does not create heat buffing does . there is a reason the step the grits the way they do .
 
When doing a singlestage job where there is going to be some blocking and buffing it is always a good idea to make sure you have more than enough material to work with. Ideally I want a minimum of two coats more than full coverage. There is nothing worse than spending the time blocking and buffing to end up with a burn through at the end. 3 coats is marginal if full coverage was achieved at 2. Also keep in mind there will mostlikely be a time down the road where you'll want to re-buff or polish wear and tear scratches or worse and the extra material provides some cushion.
 
Bob,

I agree with you wholeheartedly. If I would have known then what I do now, another coat would have been applied. I will try to keep the color in the runoff water to a minimum. If I burn through now, I will just order up another quart of paint and repaint the roof while the car is on the rotisserie. If I do not burn through I will not repaint now. With the knowledge I have learned in VO Tech and from this forum as well as what brief experience I have obtained, I am confident that if I need to repaint the roof sometime in the future, I can do it.

I know the panels have a thicker layer of paint on them than the roof. That will help my confidence when I start color sanding them. I plan to color sand just prior to reattaching them to the shell. I think it will be a lot easier to color sand the fenders, doors, etc. while in a horizontal position on the fender stands. The rear deck and hood can be color sanded after being attached to the shell.

Once again I want to thank you all for your advice and encouragement.

Charlie D.
 
Unfortunately I broke through. I will use Shines advice and hard block the roof with 800 then 2-3 more coats to make sure I have plenty of thickness to work with.

Charlie D.
 
It's not obvious from your post if you understand shine's advice, which is 3 coats more from where you are right now, hard block, then shoot at least 2 more. If that's what you mean, then disregard this post! :)
 
Crashtech/Gentlemen,

I misunderstood the advice. I planned on spraying two or three more coats over what I have now. Maybe a little more on the spot that is showing through. I need a little more assistance please. I know that it is aggravating for some of the ole’ salts on this forum to keep holding the beginners’ hands and leading them through processes that are well ingrained by experience. For what little it is worth I sing this forum’s praises to anyone that will listen. I have already been coached a lot during this body work and paint project and really appreciate it.

When going from bare metal to the spraying of the seal coat and then the finished SS Acrylic Urethane my last grit was 400. After color sanding with the 800, 1,500 & 3,000 did not work out; I had started over on the roof with 1,000 then 1,500 when I noticed a slight variation of color about the size of a quarter. The area set out by the blue tape has been sanded with 3,000. What grit should I prep the roof with before going back over it with the 3 coats of the SS? I am thinking either 600 or 800; maybe even finer? I want to make sure the 3 coats adhere well to the SS that is on it now.

I know I need to let each of them flash between coats. My question is how long to let them cure before I do the 800 wet sanding. It may depend on how wet they are? How much orange peel that has to be sanded? I appreciate your advice and help. As you know this is my first, and at 66 years old, probably last rodeo when it comes to painting a car.

Thank you for your help,
Charlie D.
 
Well think of it this way, you rubbed through last time, so it's best to plan for a greater margin of error, i.e. more paint film thickness this time around. It's very likely that you don't have very much paint left on that roof at this point. Shine's advice is a way to get the required film thickness without excessive texture, which will continue to increase with each successive coat.

Since you have already sanded the roof flat, you might want to use gray Scothbrite and prep paste to get it ready for paint. I'm a little afraid that if you choose to re-sand the whole thing, you'll have cut-throughs all over.
 
I would prep a red scotch pad or 1000grt wetsand and put 5-6 new coats of paint over what you have now. That way when you do wetsand and buff it again you should have atleast 2.5-3 coats still left on. try not to slam down each coat of paint, just nice even medium wet coats is what is needed this will also keep the heavy orange peel down leaving you with smaller peel which is easier to deal with.
Consider what paint that is there now as nothing more then a seal coat, because it is probably to thin to count as a true layer of paint so think of it as you are now just going to paint for the 1st time.
 
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